Hydrochloric acid recovery



March 13, 1951 J. E. SEEBOLD 2,545,314

HYDROCHLORIC ACID RECOVERY Filed Feb 12, 1943 2 Sheets-Sheet 1 James 5. J'eebo/d IN VENTOR.

I grromvry Patented Mar. 13, 1951 r 2,545,314

UNITED STATES PATENT OFFICE nYnRoonLoRIo ACID RECOVERY i James Edwardseebold, Chicago, Ill., assignor to Hercules Bowder Company, Wilmington, Del., a. corporation of Delaware ApplicationiFebruary 12, 1943, Serial No. 475,624

2 Claims. (Cl. 23-154) This invention relates to thema'nufacture of the absorption tower, the heat of absorption of ydrochloric acid and mo e particularly to the i the gas causes the formation of steam, which manufacture of hydrochloric acid by absorption formation in turn reduces the temperature of from waste gases containing hydrogen chloride. the rest of the liquid so that the high concentra- In one method for the manufacture of hydrotion of hydrochloric acid is formed.

chloric acid, hydrogen chloride is first formed in Having now indicated in a general way the any suitable manner as by the reaction between nature and purpose of the invention, there folsodium chloride and sulfuric acid or 'it may re- I lows a more detailed description of the preferred suit as a by-product in the manufacture of embodiments thereof with reference to the ac-, organic chlorinated materials as, for example, companying drawings in which:

chlorinated rubber. The hydrogen chloride is Figure 1 is a perspective view of an absorption thenabsorbed in water or dilute acid. tower for use with the present process; Hydrogen chloride is absorbed inwater when Figure 2 is a graph showing an observed-relaits partial pressure in the gaseous phase is greattionship between the temperature of the liquid er-than that in the liquid phase and absorption '15 at the bottom of the tower and the acid strength; continues until'the partial pressure in the gasand eons phase is equal to the vapor pressure of the Figure 3 is a graph showing an observed relagas in solution. To have this difference in partionship between the percentage of hydrogen tial pressures, at high acid concentrations, either chloride left in the tail gas and the strength of the gases must have a high hydrogen chloride the acid produced.

concentration or the liquid must have a low tem- In Figure 1 is shown an elongated cylindrical perature or both. Where h hydrogen chloride tower it, which is preferably made of iron, and content f e s is ow, the gas-liquid equ b lined with glass. The tower is packed substanu 'n po t is reached at a w d concentration tially its full length with Raschig ringsor the like a d m s r m v t at f solution, ll. At the top of the tower is the steam ejector which for the absorption of rq Fhloride l2, which may be used as needed, through which in t is Very large, must be p d 111 Order steam is passed out of the steam jet l3, thereby 9 -F ajbsorptloncreating a partial vacuum in the line I4. The Practlce W Packed e steam from the ejector l2 together with the tail sorpt on towers provided with suitable coohng gases may be passed through a condenser not means and 'Wherem gas contammg g z shown or allowed to esca e Also at the top of chloride is brought into countercurren con ac with the absorbent acid solution or with water the towel Water supply controlled by a valve l7 and having a spray head l8. One or more absorbers may be used suitably con- In the bottom of the tower is the g inlet ggggg g i fi it; iigii ggj gf m gggg connection 20 controlled by valve 2! and the acid tion of water or by recirculating some of the acid recovery plpe which leads to the hydrPmeter emuent back to the absorber or both float box 23, wherein the hydrometer 24 is used Equipment now in use for th absorption of to check the qual ty of the acid. The hydrometer hydrogen chloride is, however, subject to the disfigat box is vided wit outlet 25 for the readvantage that the provision of'cooling means moval of any matenal Whmh may separate Such is .quit expensive Since the costbf Suitable as carbon tetrachloride, and outlet 26 for the reterials is high. Furthermore, provision for coolmoflal of the f to carboys or other q ingcomplicates the construction and mainten- U Thls product l be cooled in a Sultable ance' of the equipment, thus adding to the cost. external 9 If v I If cooling is to be effected in the absorption tower Substantlally pure hydrogen chlorlde may be itself, it "is necessary to construct the tower of used but the inventin o mplates th use a so materials having a high heat conductivity, such P lily-products 0f the Chlorination of O g as the more expensive acid resisting metals. materials, such as chlorinated rubber, which con- Nw in ag dan jth'th pre t invention, '5 tain substantial amounts of hydrogen chloride gases rich in hydrogen chloride may be passed and preferably more than in order to obtain through an absorption tower without external a hydrochloric acid of about 20 Baum (about cooling means of such size, velocity and tempera- 3 HCl). Cold Water is used for absorbing the ture that 20 Baum hydrochloric acid is progas, but the heat absorption will cause the vaporiduced. No external cooling means is used. In 5 zation of a part of the Water at one point in the .drogen chloride and;v the about 05 fti/sec. 003

tower, which vaporization results in a coolin of, the fluid. The space velocity of the gas and the temperature of the entering gas and water may be so adjusted as to result in a certain temperature and strength of the acid leaving the bottom of the tower. An observed relationship between this temperature at the bottom of the tower, and the; graph at- Figure 2. From this'graph itwillbe': seen that the temperature at the bottom of the tower can in most cases be held below about 909. C. for most acid strengths.

about 37, are obtained with.mnchgooohir.solve tions, but tend to result inia-verygreainamount of the hydrogen chloride being left in the tail? Figurefir where. anobserved.

gas as is indicated in relationship between this hydrogen chloride left in the tail gas and the resultant acid strength-are:

compared.

The: following isi-an example. of: a:' method of carrying; out: the process 1.-

Example An absorptionltower substantially; of! the designshown irrFigureal was. set .up. comprising a glassfilined steeLpipe of 3: inside diameter and lagged= for.-its entire-.10 length :with 1. /2! insulation; The pipeiwaspaclred to a height &9" with Raschig rings.-. A-steamejector. was. used. for

. drlawinggthe; gases-lupward through. the column mitted. to -theitop of. the. tower. and. the. gas passed upwardly through it by means. of..the steam jet ejector: atv avelocity', of. about 1, per second; In ashort time, the .liquidat theb'ottomof "the tower hada. temperature oi. about. 70 'C. The hydro.- chloric. acid withdrawncontained about 32.%'.hy-

.tail; gases contained about of" hydrogen chloride.

Various. concentrations. of: hydrogen chloride may be usediin the entering gas, but in order'to obtain; a. commercial",concentration of hydrochloric acid (ab out '32'% in-asingle-pass; it"is preferable that the entering gas contain at least 60 of" hydrogen chloride.

The velocity of" the gas" i'n'the tower may be varied, but for the-- best yields-a velocity of'from -ft':/-sec.- should be used and preferablyabout 1 fti/sec. a contact time of from about 5to about- '15 seconds and preferably for about 10' seconds.

" The temperature-of the enteringj as may: also varied" from about: 0? Ci: to: about: 508- CL but. should preferably bei at'ab out: 2590.. In addition; the? t'emperatuteaofi the entering water. may be variedefrornabout 0?'-C'.'.to;aboutil00"- C; but should alsnrbe preferably about; 25. The-velocity: of

the gas and the water rateshouldrbe-so adjusted that'thatemperaturevat .thesbottomyof. the-tower doesinoaexceedabout. 9.0? Q. .andpreierably from about-14010; about: 705" C.

application; a5; continuation-in-pant. of

. application-for *UnitedaStatese LettersIRatent,

Serial No.. 381,287. filed. March. 1,. 1.9421,. now abandoned..-

acid; strength .is shown in. the.

The. acid. strengths... between 34 and the equilibrium point, which'is" What I claim and desire to protect by Letters Patent is:

1. A process for the manufacture of hydrochloric acid which comprises supplying water at a temperature substantially below 100 C., to the upper portion of an uncooled absorption tower, supplying a gas rich in hydrogen chloride to the lower portionof the absorptiontower 'at; a temperature substantially below C1. passing the hydrogen chloride containing gas upwardly through the absorption tower countercurrent to the-.flow, Qfcwater therethrough whereby the hydrogen chloride gas is absorbed by the water, controllingathe rateof flow of the water, the rate of fiow of said"gas-, .and the temperatures thereof so as=to maintairn the temperature within the tower. atetheientrance point of the gas substantially below 90 'C;' and the strength of the acid obtained at least about 20 B.- (about 32%) allowing the heat of absorption of the hydrogen chloride. .im the:- water? tea-evaporate: a. portiom: of the water;inj-thez-towen; applyingpartial vacuum to: evaporate; additional watenand to withdraw ansamolintiofzwater vaporirom the-:upper'portion' Ofithii towers-which: contains as. latent heat-.3 of vaporization. anarnountzof heat: .w-hicnis -a.;s.ub.- stantial' proportioniof; the-heat ofaabsorpt-ion evolvedcim the tower, and-withdrawing: from-i the bottomzofz the. towenian acid-with :a. concentration oi: at-.:1east1about::;32%l by: weight: of hydrogen. chloride...

2. A process: forzthewmanufacturezof strong hydrochlericacid. which comprises-fiowinQmgas containing morexthang- 60%; by--weight hydrogen chloride: at actemperature; of about 25? C;v to; the:

bottom. of; amuncoolediabsorptioni tower; supplying water. atza; temperaturezof iabout:25 GI. tat-he.

,REEERENGES. GIIED,

The following references :areof I record? in"; the file:- of this patent:

UNITED, STATESJPATENTS" pp. 3101412,- Guerneyfilzf Jackson; liondqni'. Engrland}; 

1. A PROCESS FOR THE MANUFACTURE OF HYDROCHLORIC ACID WHICH COMPRISES SUPPLYING WATER AT A TEMPERATURE SUBSTANTIALLY BELOW 100* C., TO THE UPPER PORTION OF AN UNCOOLED ABSORPTION TOWER, SUPPLY A GAS RICH IN HYDROGEN CHLORIDE TO THE LOWER PORTION OF THE ABSORPTION TOWER AT A TEMPERATURE SUBSTANTIALLY BELOW 90* C., PASSING THE HYDROGEN CHLORIDE CONTAINING GAS UPWARDLY THROUGH THE ABSORPTION TOWER COUNTERCURRENT TO THE FLOW OF WATER THERETHROUGH WHEREBY THE HYDROGEN CHLORIDE GAS IS ABSORBED BY THE WATER, CONTROLLING THE RATE OF FLOW OF THE WATER, THE RATE OF FLOW OF SAID GAS, AND THE TEMPERATURES THEREOF SO AS TO MAINTAIN THE TEMPERATURE WITHIN THE TOWER AT THE ENTRANCE POINT OF THE GAS SUBSTANTIALLY BELOW 90* C. AND THE STRENGTH OF THE ACID OBTAINED AT LEAST ABOUT 20* BE. (ABOUT 32% ALLOWING THE HEAT OF ABSORPTION OF THE HYDROGEN CHLORIDE IN THE WATER TO EVAPORATE A PORTION OF THE WATER IN THE TOWER, APPLYING PARTIAL VACUUM TO EVAPORATE ADDITIONAL WATER AND TO WITHDRAW AN AMOUNT OF WATER VAPOR FROM THE SUPPER PORTION OF THE TOWER WHICH CONTAINS AS LATENT HEAT OF VAPORIZATION AN AMOUNT OF HEAT WHICH IS A SUBSTANTIAL PROPORTION OF THE HEAT OF ABSORPTION EVOLVED IN THE TOWER, AND WITHDRAWING FROM THE BOTTOM OF THE TOWER AN ACID WITH A CONCENTRATION OF AT LEAST ABOUT 32% BY WEIGHT OF HYDROGEN CHLORIDE. 